All his life, with his habitual passion for accuracy, Mercator had been squirreling away maps and reports from the expeditions that had extended the boundaries of the known world during the previous eighty years. He was in touch with other mapmakers and geographers across Europe and beyond—for example, he regularly exchanged letters with a Portuguese scholar-monk named Philip Sassetus who lived in Goa, on the Indian coast—and John Dee was only one of many foreign scholars who came to see him, as eager to meet the great man as he was to pump them for information. Mercator described later how he had prepared the ground, comparing Spanish and Portuguese charts with each other, and then studying other printed and handwritten accounts from past centuries, patiently reconciling Spanish with Portuguese, past with present. "It is from an equitable conciliation of all these documents that the dimensions and situations of the land are given here as exactly as possible," he wrote in the legend to the map.
The maps of the Spanish and Portuguese explorers and of the English expeditions to the North—or at least descriptions or summaries of them—were the pure gold that cartographers like Mercator sought, but there was also valuable information to be gleaned from the portolan charts drawn up by professional seamen to make their own regular journeys more reliable. The navigatorias chartas to which Mercator had referred in his letter to Granvelle were almost certainly such hand-drawn seamen's sketch maps. The two trades, chart maker and cartographer, had grown up separately, but what the seamen's charts, or cards, lacked in sophistication, they made up for in hard-won and up-to-date experience. It is impossible to say how many such charts3 reached his desk, but these were what he was hoping for in return for the help he had given John Dee in planning the English voyages to the Far North; Mercator's son Rumold, who was working for a bookseller in London, also did his best to find what pieces of information he could.4The sketches, distances, and descriptions contained in such maps and in the written directions that often accompanied them were "equitably conciliated" along with Mercator's other information.
Ever since he had produced his first globe in 1541, he had been tackling the problem of projection in reverse—preparing flat maps that had to be shaped and pasted to fit a spherical globe. He had seen how the wet, pasted map could stretch if not handled properly, pulling all the lines out of shape. Calculating the curve of the individual gores and cutting them precisely was as much a problem of manual dexterity as of intellect, but such work had left him constantly aware of the limitations of Ptolemy's theories of projection. By considering the Earth as a cone to be unrolled, Ptolemy had forced the lines of longitude out of true, making them converge some distance above the pole. That led to significant distortions of direction on maps drawn according to his prescription; but then, straightening the lines of longitude so that, as parallel lines, they never converged at all would necessarily stretch the lines of latitude and lead to still more inaccuracy. But what if the distances between those lines of latitude were to be altered in the same proportion—if the map were to stretch not randomly, as had occurred when he pressed the wet gores against the plaster coating of his globe, but proportionately, in every direction at once? Then the distances between places, the sizes of islands and continents, would be exaggerated, but their positions relative to each other would remain true.
Mercator went back beyond Ptolemy to the older and simpler cylindrical projections. First he straightened the meridians of the globe, so that, instead of meeting at the North and South Poles, they continued as parallel lines on his map, just like those of the original rectangular graticules of the ancient Greeks. Doing that necessarily stretched east-west distances on his map as it got closer to the poles, and also distorted the directions in the same proportion—lines of latitude, which grow progressively shorter on the globe, were shown as equal in length.5The resulting exaggeration of distances as the map approaches the poles is a feature of any cylindrical projection. However, maintaining the true direction was Mercator's priority, and so he next extended the gap between his lines of latitude in the same proportion as he had earlier moved apart the meridians. On the map, that results in lines of latitude appearing farther apart the closer they get to the two poles—and as a result, the distances Mercator showed were grossly distorted in the polar regions. Islands such as Greenland and Spitzbergen were—and are—shown much larger on a Mercator map than in real life.
Mercator had intended that his map of the world be used at sea, not just in the study. And the title of the map leaves no doubt about this:Nova et aucta orbis terrae description ad usum navigantium emendate et ac-comodata (a new and improved description of the lands of the world, amended and intended for the use of navigators).
Thus, though the distances may have been expanded, the directions on his map precisely reflected the course a navigator would need to steer on the sea. For sailors and navigators, the relative size of the lands they sailed to would be a matter of little importance compared with the ability to follow a straight course across the map. As a practical matter, the fact that Europe appeared bigger on the map than the mysterious and unexplored lands in the tropics was a positive advantage to a cartographer who had much more information to include about the lands close to home compared to what he knew about the equatorial region. Mercator's was a Eurocentric map for a Eurocentric age.
Today, with the advantage of hindsight, his innovation—like many other great discoveries—strikes us as beguilingly straightforward. In essence, he was simply lengthening the lines of latitude and of longitude in equal proportions; any one of the cartographers who had wrestled with creating a world map in the centuries since Ptolemy might have done the same. Ironically, it was in part Ptolemy's own achievement in setting out his suggested projections that had prevented them: In a world where few long journeys were made to the Far North or South, there had for centuries been little incentive to produce a map like Mercator's. Ptolemy's projections were good enough for the world he knew, and, with minor adjustments such as those of Waldseemiiller, they were acceptable for much of the sixteenth century. The English explorations of the northern seas had exposed their true limitations, and Mercator's map was drawn at a time when the need for a new projection was becoming clear.
The new projection had its own limitations. It could not, for example, show the shortest distances for long voyages. That could be demonstrated by stretching a piece of string around the globe between the point of departure and the destination, and would have appeared as a long curve on Mercator's map. Actually following such a course—the so-called great circle route—involves so many changes of compass bearing that it would have been practically impossible for sailors with the skills and instruments of the sixteenth century. Mercator's map, then, offered an alternative that was both reliable and simple.
Previous projections were simply not adequate to map the world that the explorers had revealed. Mercator summed up the problems with traditional maps that navigators on expeditions to the North had noted: "It is inevitable that the shape of the lands is enormously distorted, and that for this reason not only longitudes and latitudes, but also directions and distances are far from correct. Great mistakes result."6 On his map, the problem of distances remained, but those of longitude, latitude, and—crucially—direction had been solved.
Like Brunelleschi working out the technique of perspective drawing a century and a half before, Mercator left no notes or clues to the process by which he arrived at his great discovery. For all Walter Ghim's boasting that he watched him at work on his map, the real preparation of the new projection was done in private. Whether it was calculated from mathematical first principles or worked out by trial and error is not known. Although an accomplished mathematician like Mercator must have had some idea of the theoretical basis of what he was doing, he most likely drew the projection with geometric instruments such as dividers and protractor—mechanically, rather than theoretically.
ONLY THREE COPIES REMAIN today of the map that emerged from Mercator's lengthy process of gossiping,
checking, comparing, and designing. One, colored and bound into an atlas by a later hand, is in Holland, at Rotterdam's Maritime Museum. Another is in the university library in Basel, Switzerland. The third is kept at the back of an office storeroom in Paris's Bibliotheque Nationale, hanging in a rack with other maps, almost like washing on a line. Here, Mercator's work can be viewed as he intended. The eighteen individual sheets have been carefully pasted together to make a large map (523/4 inches wide by 83 V2 inches long). Reproductions in books, though, are no substitute for the delicacy and scale of the real thing.
At first sight, the map is oddly unimpressive. The Hereford mappamundi, with its deep ochre coloring and the strange, idiosyncratic world it portrays, gives an immediate sense of great age. Mercator's map of 1569 may mark a turning point in people's appreciation of the world around them, but at a glance it seems little more than a simple black-and-white line drawing, with notes, sketches, and brief essays all jostling for attention. Only when one climbs the stepladder to study it more closely are the map's intricacy and detail revealed. The Amazon River snakes through the interior of a strangely bulbous South America, and delicately drawn dense forests cover much of Russia. The former Aztec capital of "Tenuchtitlan" is marked in Central America, as are, farther south, the Incas' ancient city of Cuzco and also Lima, the thirty-five-year-old settlement of their Spanish conquerors. Much of the rest of the world is dotted with towns and settlements; some of them, like Exeter, York, Paris, or "Duysborg" itself, are well-known, but others, filling the center of Africa and the deserts of Arabia, never existed. For all Mercator's careful researches, this map, like the Hereford one, was in part a compendium of what people believed.
The sketches of biblical stories, which were such an important feature of the maps of the Middle Ages, are gone, but Mercator could not restrain himself from adding a few drawings depicting other, more modern, tales and fables: In South America cannibals are cutting up and cooking an unfortunate victim, and a strange kangaroolike animal is suckling its young; in the middle of Africa the mythical Prester John sits serenely at the center of his empire.7
LIKE THE HEREFORD mappamundi—like all maps—Mercator's world map is a self-portrait as well as a depiction of the world, reflecting the age in which it was conceived. For all its creator's personal religious devotion, Christianity no longer held an unchallengeable, overarching role in European society. On most maps, Jerusalem had lost its medieval place of honour at the center of the world a century or more earlier; on Mercator's, it can barely be found at all, the tiny letters Mm squeezed in among the other biblical names. The Holy City had been reduced to an abbreviated afterthought.
Instead of the reliance on God and the Church that the medieval mapmakers exhibited, Mercator's map depicts a world that is confident in itself. The towns that fill Europe, Africa, and Asia, whether real or imagined, suggest a landscape that has been tamed. The scattering of names in the areas of Spanish influence in the New World and elsewhere, as well as the empty spaces—vast areas of America and Russia without a town in them—speak of a conviction that European culture will eventually spread there too. Even the huge sea monsters with which Mercator decorated the Atlantic and the Pacific don't seem to pose a threat to the ships plowing the treacherous seas. This, the map seems to say, is the age of trade, which will carry all before it.
In the Eastern Hemisphere, Mercator had thirty years of exploration on which to draw since his last map of the world, and the coastlines, particularly in Southeast Asia, are much more recognizable today than those he had drawn in 1538. To the west, America was no longer the mysterious and intriguing land it had been. Repeated voyages across the Atlantic and around Cape Horn had revealed much of its coastline. While many geographers were still arguing about whether the new continent was simply an extension of the Asian landmass, Mercator had no doubt. "Those who say that New India continues with Asia are mistaken," he declared,8confidently drawing in the west coast of America and the whole Pacific Ocean.
In his depiction of America, Mercator provided more details than ever before. Although the squat, bulging outline he drew of the southern half of the continent may appear grotesquely distorted, the western coastline of North America was much more accurately drawn on his map than it had been earlier. Seven years before, the Spanish cartographer Diego Gutierrez9 had produced a wall map of America that showed nothing of the northern half of the continent beyond the eastern seaboard. Mercator, by contrast, depicted a long sweep of western coastline, including the peninsula of Baja California, which Waldseemiiller and other cartographers had shown as an island, and also attempted to show mountains and rivers in the hinterlands of both North and South America.
Anyone looking at Mercator's map for the first time would have been struck by the size of the new continent. America seemed to have swallowed up a quarter of the world. On earlier maps, including his own, it had looked small and unimportant, but on the map of 1569, it had swelled to fill almost half of the Northern Hemisphere. New information from the voyages to the Americas had led Mercator practically to double the width of the northern part of the continent from 80 degrees on his first world map to around 155 degrees on this one.10This revision reflected Mercator's realization of the huge scale of the discoveries that were being made in the Western Hemisphere; it was also a shrewd way to recognize Spain's King Philip, whose domains in the New World were shown stretching impressively across more than 40 percent of the globe, a graphic representation of power.
But there was more than new information and political circumspection to explain the huge increase in size of North America. Because of Mercator's projection, which progressively increased the linear value of each degree of latitude and longitude as the map extended north and south, the sixtieth parallel, which ran across the widest part of what is now Canada, was twice as long on the new map as it should have been. He believed that the continent extended nearly twice as far around the globe as he had thought before. In addition, as a result of the projection, each degree of its breadth stretched twice as far as it had on his earlier map. Mercator's projection had turned America into a monster.
The same thing had happened to an even greater extent at the bottom and top of the map. Ptolemy's influence remained: Like Waldseemiiller some sixty years before him, Mercator had followed the Greek master in drawing the great southern continent that reached almost to the tip of South America—"the Southern Lands, not yet discovered at all," as one early map put it, with appealing ingenuousness. Mercator had drawn this mythical continent on his earlier world map, separated from South America by the narrow Strait of Magellan, with Tierra del Fuego a headland rather than an island, and he had no reason to change his mind. The long, sweeping, and entirely imaginary coastline almost reached the southern coast of Africa and the East Indies. The sheer extent of this land was striking: It ran from one side of the map to the other. It would have to exist, Mercator reasoned, in order to balance Africa, Asia, and Europe, and maintain the equilibrium of the globe."11
In the North, a similar belt of land extended above North America and Russia. For all the efforts of the English explorers, the North Pole remained in practice, like its southern counterpart, unseen and unseeable, but with this new projection, both poles were also unmappable. At the points where lines of longitude converge on the globe—the two poles—degrees of latitude and longitude alike were stretched to infinity.
This was only of theoretical interest, as no explorers of the sixteenth century were going to reach either pole, but in the North, Mercator tried to meet the difficulty by including a small inset, drawn from a different viewpoint from that of the rest of the map. From directly above the pole, he showed a group of four islands, separated by rivers running into the "indrawing sea" that covered the pole itself. At its center, at the point where the waters were sucked into the depths of the Earth, stood Mercator's mythical rupes nigra, the black rock that he believed was the source of the Earth's magnetic field.12In the legends to the map, he added stories
of strange pygmy tribesmen, myths of ships drawn toward lodestone mountains, and horrified accounts of irresistible storms and currents in the Far North. With no firm information from sailors to draw on, Mercator had to rely on tradition and superstition, which had coalesced to produce a grotesque tale that could have been told by Herodotus more than a millennium earlier.
Other gaps and glaring errors remained. Much of the unknown hinterland of North America was conveniently hidden behind a rectangular block containing the legend to the map; the vexed question of whether a northwestern passage to Asia existed was avoided with the aid of a carefully placed and heavily decorated dedicatory panel, although Mercator was more confident in showing a simple eastern route along the northern coastline of Russia. The search had been going on unsuccessfully for sixteen years when the map appeared, but he had no doubt that some future expedition would find its way past the frozen islands and ice-bound seas into the warm waters that lay beyond. Many of the rivers of the Americas, like those of Africa and much of Asia, were drawn from imagination or from ancient tales, as they had to be.13Exploring coastlines was one thing, but several centuries would pass before expeditions reached and surveyed the hinterland of the new continent.
For all his insight and innovation, Mercator still protested his loyalty to traditional authorities. On the legend to the map, he maintained that the Portuguese explorations in the East had provided no improvement on Ptolemy's classical descriptions, and yet a glance at Ptolemy's depiction of the coastlines of India, Ceylon, and the whole of southern Asia shows how inferior was Ptolemy's knowledge. Mercator's version of the coastline, based largely on the reports he decried, follows broadly the lines that we know today to be accurate. In the same way that he embraced religious reform without ever explicitly rejecting the traditional role of the Catholic Church, so he revolutionized the picture of the world without once denying the authority of the classical geographers.
The World of Gerard Mercator Page 21